I was talking with one of my colleagues about my column last week on cancer and they made the comment: "You can't really cure cancer."
They are right.
As I said last week, cancer comprises a myriad of diseases and affects people in very different ways. It is not a singular disease. It results from DNA damage and as long as the potential for DNA exists, then some cells will become cancerous.
It is not like a cold or pneumonia or a host of other diseases that afflict people every day. There isn't a vector. No bacteria or viral agent that we can destroy, in most cases.
We have been so successful in eliminating small pox, polio, tuberculosis, and other diseases because there was a specific organism that we could wipe out. Once the causative agent has been eradicated, the disease is no longer present in the human population.
(Of course, this requires constant vigilance in order to ensure that the disease doesn't re-emerge. Hence, the need to keep vaccinating children against disease. The bacteria or virus is not gone - it's just not actively producing disease. If we let down our defenses, it will re-emerge as in the case of rubella that have been cropping up in some regions of British Columbia.)
In any case, most cancers are an internal issue where programming in the cell has gone wrong and the cell divides unchecked. They can not be eradicated with vaccines nor can they be cured in the same way. An anti-cancer antibiotic would have nothing to act on except the host's body and that is fraught with difficulty.
There is a small percentage of cancers - about 5 per cent - that appear to be caused by a virus, such as the human papillomavirus. The development of vaccines for these cancers is possible, preventing the disease in the first place and with a rigorous program of vaccination it is possible that HPV will eventually be eradicated.
Of the remaining 95 per cent of cancers, there is some hope that as our understanding of the basic biochemistry of the cell develops, treatments will emerge that will stop cancerous cells from developing and spreading. We might be able to stop people from developing cancerous cells but we may be able to stop the cells from becoming a tumor and being fatal.
One such hope is the gene TP53 which produces a protein called p53. It is an unfortunate name as it doesn't really mean much other than it is a "protein that has a mass of 53 kiloDaltons". In fact, it is actually only 43.7 kDa in size.
But despite the unassuming moniker, there are some researchers that view p53 as the guardian of the cell's genome and, by extension, the best hope for controlling cancer. p53 is a tumor suppressor in humans.
Under normal conditions, p53 is inactivated by a negative regulator, called "mdm2". As long as there is enough mdm2 around, p53 remains quiet. However, when damage occurs in the cell or to the DNA, other molecules effectively reduce the amount of mdm2 and p53 kicks into action.
In its anti-cancer role, p53 can do one of three things. It can activate the DNA repair proteins directly and immediately. It can also arrest cell growth at a point in the cycle called G1/S and hold it there until repairs to the DNA can be accomplished. Then the cell can continue replicating.
The third possibility is that if it finds the DNA to be irreparable, it initiates apoptosis or programmed cell death. Essentially, it tells the cell to commit suicide.
The activation of p53 occurs in response to a myriad of stress types, aside from DNA damage by UV light or by chemical agents, such as osmotic shock, oxidative stress, ribonucleotide depletion, or deregulated oncogene expression. In essence, it is a protein that has evolved to protect the genome.
The importance of p53 to the growth of tumors is observable in the negative form. That is, in about 50 per cent of cancerous tumors, the TP53 gene that encodes for the protein is damaged. Further, people who inherit only one functional copy of the gene are more likely to develop tumors in early adulthood, a disease known as Li-Fraumeni syndrome.
So, can't we just replace the damaged gene? Not yet as it is present and active in every cell in the body. Nor can we simply supply people with the protein as it is readily degraded in the cell. It is a regulated protein.
The answer, of course, is to avoid activities that can lead to DNA damage in the first place. Avoiding exposure to UV light or carcinogenic compounds such as the compounds in cigarette smoke are a good starting point. But some of us inherit bad genes in the first place.
In the end, cancer will likely always be with us. With early detection and better treatment techniques, though, it does not have to be a deadly disease.
